Flash boiler control



March 20, 1934. w. DOBLE' 1,951,350

- FLASH BOILER CONTROL 7 Film} March 23. 1931 2 Sheets-Sheet 1 INVENTOR.[Var/"er; Dob/z ATTOR March .20, 1934. w. DOBLE FLASH BOILER CONTROLFiled March 25, 1931 2 Sheets-Sheet 2 INVENTOR.

I War/e77 006/2 ATTORNEYS.

Patented Mar. 20, 1934 FLASH BOILER CONTROL Warren Doble, Emeryville,Calif.

Application March 23, 1931, Serial No. 524,668

11 Claims.

This invention relates to the control of a boiler of the type which hasbeen characterized as a flash boiler but which can be also classified,and possibly more accurately, as a forced circulation boiler. Such aboiler comprises a relatively long tube. In one size the tube is aboutsix hundred feet in length and is wound into a series of coils,

water being forced into one end of this coiled tube to supply a workingfluid. Steam issues from the other end when the tube is heated,generally by passing the products of combustion from a suitablymaintained fire over the tube.

This invention is particularly concerned with the regulation and controlof the water admitted to the tube to maintain the steam issuing from theboiler substantially at a predetermined temperature and pressure at alltimes during operation of the boiler.

As is disclosed in the co-pending application of Warren Doble, SerialNo. 221,262, filed September 22, 1927, and entitled Normalizer, theintroduction of a small amount of water into the tube at a considerabledistance from the main water inlet or foot has been found to beeffective in maintaining the steam delivered very close to apredetermined temperature, the injection of the water being controlledby a thermostat responsive to a condition within the boiler, such as thetemperature of the boiler tube or the steam within the tube. However,the functioning of this structure, while very successful, neverthelessincludes the difficulty that the primary water introduced into thefootor inlet end of the tube is apt to be in excess of, or less than, theamount of water actually required, due to widely fluctuating loads uponthe boiler. Since such boilers are most advantageously used inautomotive practice for vehicles such as automobiles and rail cars wherethe load varies rapidly, the boiler may be either flooded or locallyover heated in the primary portion, that is the portion of the tubebetween the foot and the normalizer inlet. While the normalizerregulates the temperature of the steam being emitted from the boiler,the normalizer does not prevent the Overheating of sections of theboiler in advance of the normalizer inlet nor can it increase thetemperature of the steam passing the thermostat should the steam bebelow the critical temperature at which the thermostat is set.

Since such boilers are ordinarily operated under pressures between 500and 2500 pounds per square inch and since the span of operating pressurecan vary more than 2000 pounds per square inch, the overheating orflooding is a material factor in securing efiicient operation while theoverheating of localized sections aifects the safety of the boiler tube.

The control of the boiler must also take into account the desirabilityof having the heat supply for the boiler an intermittent one. In onesuccessful form of boiler, the heat is furnished by blowing an airstream through a carburetion which is subsequently ignited and blowninto the boiler to pass over the coiled tube. The blower for supplyingthe air operates intermittently an the fire accordingly is periodic.

It is therefore the general, broad object of the present invention toprovide for the control of a forced circulation boiler so that localizedoverheating or flooding of the boiler are prevented, while steam of theproper temperature and pressure is produced.

The foregoing and other objects are attained in the embodiment of theinvention shown in the drawings, in which Figure 1 is a schematic viewillustrating a forced circulation boiler and a feed control embodyinggny invention.

Figure 2 is a schematic view illustrating a forced circulation boilerand a modified form of control of my invention.

My invention includes the provision of a device for controllingthe'introduction of water into a boiler by means of which steam isfurnished by the boiler at a substantially uniform temperature withouthaving either overheatingor flooding of the boiler occur. Particularly,my invention contemplates the utilization of the normalizer principlepreviously disclosed and a primary or main feed water control of such anature that overheating and flooding are obviated.

The form of the invention shown diagrammatically in Figure 1 provides arelatively'long tube 6, in one instance approximately six hundred feetin length, which is wound into a plurality of coils and is disposedwithin a suitable outer casing 7 to absorb heat. The heat isconveniently secured from products of combustion formed upon ignition ofa fuel-air mixture directed into the boiler casing through a venturi 8by a blower 9 which forces air over a carburetion device 10. Thefuel-air mixture is ignited by a suitably energized spark plug l1,'theproducts of combustion passing counter-current to the fluid in the tube6. Water is injected into the foot or inlet 12 of the boiler and iswithdrawn as steam through outlet 13 under-control of a throttle valve4. The products of combustion able automatic devices responsive toboiler conditions and, preferably, the blower 9 and the ignition of thefuel-air mixture are controlled in accordance with the temperature andpressure in the boiler. To this. end a temperature device, such-as athermostat 21, is provided which is responsive to a condition within theboiler, for instance, the temperature of the boiler tube. A pressuredevice 22 is also provided to be responsive to steam pressure in theboiler. The temperature device 21 includes a rod 23 adapted to bear uponand position a spring biased rocker 24. Spring biased contact arms 26and 27 depend upon the movement of the rod 23 and the rocker 24 to openor close certain electrical circuits. I

The contact arm 26 is included in an electrical circuit with a battery28, one side of which is grounded, a master switch 29, contacts 31 and32 controlled by the pressure device 22, contacts 33 and 34 controlledby the contact arm 26, a spark plug 11, and an electric motor .35 forthe blower 9, one side of the spark plug and of the blower motor beinggrounded.

The other contact arm 27 carries a contact 36 cooperatively positionedwith a contact 37. These contacts control a circuit including in seriesthe contacts 31 and 32, the master switch 29, the battery 28, and agrounded solenoid 38 for operating the normaliz'er valve 39.

The temperature device 21 is so constructed that when the boiler tube isat a low temperature the contacts 33 and 34 are in abutment. When themaster switch 29 is closed and the pressure in the boiler is low so thatthe contacts 31 and 32 on the pressure device are in abutment, cur rentflows through the contacts 31 and 32, and contacts 33 and 34 to theblower motor 35 to inject a fuel-air mixture which is subsequentlyignited by the simultaneously energized spark plug 11, whereupon heat isavailable" in the boiler to generate steam.

When the temperature rises above a predetermined or desired value, therod 23 forces the rocker arm 24 to permit contacts 36 and 3'? to abut sothat the solenoid 33 is energized to open the normalizer valve 39 andadmit a stream or slug of water through a pipe 21 into the boiler tubejust in advance of the thermostat 21. This water tends to reduce thetemperature of thermostat 21 below the predetermined value, andconcurrently reduces the excessive temperature of the passing steam.Such reduction affects the thermostat 21 and causes the rocker 24 againto open contacts 36 and 37. Since the'movement required for this purposeis small, contacts 33and 34 are not disturbed. With the opening ofcontacts 36 and 37, the solenoid 38 is deenergized,- the valve 39 isclosed and thefiow of normalizer water is stopped, whereupon'thetemperature of the" thermostat again begins to rise above thepredetermined value. The opening and closing of the contacts 36 and 3'?can repeat an indefinite number of times until the temperature of thethermostat drops materially below the predetermined value, during whichtime the boiler is said to be flooded or until the temperature risesmaterially above the predetermined value at which time the thermostat21, opens the contacts 33 and 34 and interrupts the supply of heat,after which the temperature drops and the cycle repeats. The temperatureof the outgoing steam is thus kept substantially uniform, in practicebeing maintained within one 7 or two degrees Fahrenheit of the desiredvalue. If at any time during the operation of the boiler, the pressureexceeds the value for which the device 22 is adjusted, the contacts 31and 32 are opened and the circuit to the blower motor 35 and the sparkplug 11 is broken thus stopping the supply of heat and preventingfurther pressure rise. While the above described control system iseffective to maintain the temperature of'the outgoing steamapproximately at a desired value, it is not effective if the steamarriving at the thermostat is very low in temperature nor to preventoverheating of the primary portion of the boiler tube especially justin'advance of the I operation is erratic, particularly wherethe load Ion the boiler fluctuates. The boiler .tube may be alternately overheatedwith a liability of failure of the tube or a considerable length of thetube may be filled with water, with the result that the temperature ofthe steam issuing from 1 the tube subsequently falls far below thedesired value.

Since in one design the boiler tube is about six hundred feet in lengthand the temperature responsive device is positioned about thirty feetfrom the outlet end, water injected into. the inlet end or foot mustpass through about five hundred seventy feet of tubing before coming tothe temperature responsive device. A period of time of the order of atleast six seconds usually elapses before this distance is traversed.This time lag is too great for satisfactory andprecise control underadverse or unusual conditions.

In accordance with my invention I provide a boiler control system forsecuring steam substantially at the desired temperature under allconditions. In the system as shown in Figure 1, I position a secondtemperature device 46 in the primary portion of the .boiler tube,preferably immediately in advance of the normalizer inlet 41, so thatthe thermostat 46- is responsive to a condition within the boiler, forinstance either the boiler tube temperature or the steam temperaturewithin the tube. This thermostat 46 acts so that upon an extraordinarytemperature being present at this point, the water admitted to the tubeat the foot is controlled. The temperature device 46 includes a rod 47which acts upon a bell crank 48 for moving a valve rod 49 relative to avalve seat provided in the water inlet control valve 51.

When the temperature of the thermostat 46 is relatively low, the flow ofwater to the boiler is shut down or throttled to the rate correspond ingto that temperature. When the temperature responsive device 46 responds.to -a higher temperature, the valve is opened-to admit more der beingin communication with one side of the valve 51 through a pipe 58 and theconduit 19. The opposite end of the cylinder is connected to the otherside of the valve 51 and with the inlet of the boiler tube through apipe 59. The piston 56 preferably carries a piston rod 61 which isjoined to a lever 62 for actuating a control valve 63. This controlvalve regulates operation of the water pump 1'7 by controlling the fluidoperating the pump, in this instance steam drawn from the outlet 13 ofthe boiler through a conduit 64.

The pressure drop established across the valve 51 is that maintained bythe spring bias placed upon the piston 56 so that the flow of waterthrough the valve is proportional to the opening therethrough, whichinturn is proportional to the temperature to which the temperatureresponsive means 46 is accommodated.

In Figure 2 there is shown an arrangement in every'respect identical tothe arrangement shown in Figure 1 with the exception that the conduits58 and 59 are joined by a conduit 76 which is in parallel with theconduit 19. Controlling flow through the conduit '76 is a valve 77 whichis actuated through a crank 78 by a rod 79 extending to a similar crank81 on the throttle valve 4. The arrangement of the valves 4 and '77 andof the cranks 81 and 78 is such that when the valve 4 is closed thevalve '77 likewise is closed and that increments of opening of the valve4 pro-- '76 as controlled by the valve '77. The water now into theprimary portion of the boiler, that is, the

portion between the letters A and B in Figure 2,

is entirely controlled by the two valves 51 and 77 while water fiow intothe secondary portion of the boiler, that is, between B and C in Figure2,

. is entirely controlled by the fiow through the normalizer inlet 41.

In considering a control system for aboiler of this type it is advisableto consider the primary portion and the secondary portion of the .boilerseparately. The primary portion is filled mainly with water andsaturated steam while the secondary portion is filled mainly withsuperheatedv steam. The control-merely of the primary portion of theboiler is insufiicient properly to control the temperature of thedelivered steam since any variation in the flow of primary water is longdelayed in changing the temperature of the delivered steam. Further,when such a change has once been initiated it causes a large change intemperature of delivered steam dueto the long delay. For instance, if itis assumed thatthe boiler is producing steam at a relatively constantrate and with a slight deficiency of primary flow then the temperatureof the delivered steam gradually would rise. Should this cause anincrease in the primary flow of water then a great deal of primary waterwould be introduced into portant reason is that as the point in theboiler the boiler before the temperature of the issuing steam would beeffected. The principal reason for this is that the increase of flow ofprimary water causes a slight increase of pressure within the boilerand, because the large or primary portion of the boiler is filled withan elastic mixture of steam and water,.the compression of this mixtureprovides ample space for the addition of considerable extra primarywater. A second im- 85 at which the last drop of water is converted intosteam advances toward the delivery end of the boiler due to theintroduction of additional primary water, the thermostat located in theboiler vis not promptly responsive to. such action and before thethermostat reduces the flow of primary water a considerable delay hasoccurred and the boiler then contains more water than it is able togenerate into superheated steam at the proper temperature with theresult that the temperature of the delivered steam drops sud-. denly andflooding occurs. This cycle may repeat so that the delivered steamfiuctuates widely in temperature.

For example, taking a practical instance I have found that thetemperature at the point B can vary between wide limits, namely, betweenabout 600 degrees Fahrenheit and 900 degrees Fahrenheit, while duringsuch variation the temperature of the delivered steam from the boilerremains exactly at 900 degrees Fahrenheit. This result is accomplishedby injection of the normalizer water through the normalizer inlet 41.The temperature of steam passing point B controls the amount of timethat secondary or normalizer water is entering at point B. If-the steamcoming to this point is relatively hot it requires a greater total ofsecondary or normalizer water to lower it to the desired temperature atthe outlet of the boiler. If the steam at point -B is relatively coolerit requires relatively less such a change in the primary water flow thatconsiderable time elapses {before the effect is had on the primarythermostat 46. g

In some installations of boilers of this type there mustbe deliveredwidely varying quantities of steam and consequently Widely varyingquantities of heat are released to the boiler tube 6. In someinstallations exhaust steam from the main engine operates a steamturbine for driving the blower 9 in addition to the electric motor 35 sothat as the quantity of steam being exhausted through the outlet 13 isincreased the fire is likewise and .correspondingly increased. It istherefore necessary to increase the flow of primary water into theinlet12 largely in accordance with the increased heat of the fire- Forthis reason the valve 51 is incorporated in the water inlet line to thefoot of the boiler. As particularly indicated in Figure 2 bothnvalve 51and valve 77 are included in the system. Valve '77 is disclosed asoperated by the throttle which controls the fiow of steam issuing fromthe boiler. 150

I With this mechanical connection between the such as the thermostatactuated valve 51 for slowly accommodating any accumulated inaccuracy ordisparity between the flow of primary water and the heat of the fire.

If it be assumed that the vehicle being propelled with the describedpower plant is an automobile and if it be further assumed that thethrottle valve 4 controls the flow of steam to the main engine then aseries of rapid accelerations might result in an accumulatedinsufliciency of primary water flowing through the foot 12 of theboiler. Such accumulated insufliciency would cause a gradual heating ofthe thermostat 46 which, then, would gradually open the valve 51 tosupply a greater amount of primary water. If, however, an excessiveamount of primary water were forced into the boiler such excess wouldresult in a drop in temperature of the thermostat 46 which would thendiminish the flow through the valve 51. Although such fluctuations intemperature of the thermostat 46 are relatively slow and are much tooslow to be entirely relied upon for the complete control of the boiler,they nevertheless maintain the temperaturein advance of the normalizerinlet 41 within the correcting range of the thermostat 21. As a furtherexample, if it is assumed that the cleanliness of the heating surface isinfluenced by a deposit of soot making the boiler less efficient thenthe temperature at the thermostat 46 would be somewhat lower and wouldcorrespondingly diminish the quantity of primary water to meet thiscontingency.

If, for any reason, the temperature at the point 46 becomes unduly highthe movement of thermostat 46 opens the contacts 82 and 83 therebybreaking the circuit to the blower 35 and interrupting the supply ofheat.

In both forms of the flash boiler control system of my invention thereis provided means for regulating accurately the temperature of thesuperheated steam issuing from the boiler outlet despite widefluctuations and great variations in the operating conditions of theboiler.

It is to be understood that I do not limit myself to the form of theflash boiler control shown and described herein, as the invention, assetforth in the following claims may be embodied in a plurality offorms.

I claim:

1. A flash boiler control comprising a tube, means for heating saidtube, a first means for injecting water into one end of said tubewhereby said water flows through said tube and is converted into steam,a second means for injecting water into said tube to mix with the steamthere in, a thermostat controlling said second means, and a thermosatresponsive to the temperature of said steam prior to the mixture ofwater therewith for controlling said first injecting means.

2. A flash boiler control comprising a tube,

means for heating said tube, a thermostat re-v sponsive to temperaturewithin said tube, means of said tube.

4. A flash boiler control comprising means for defining a course forfluid, means for introducing fluid to 'said course at the initial pointthereof,

means'for introducing fluid to said course at an intermediate pointthereof and means responsive to a thermal condition between said initialpoint and said intermediate point for controlling the introduction offluid at said initial point.

5. A flash boiler control comprising a tube,

1 means for heating the tube, means for supplying primary water to aninlet" in the tube, means for controlling the primary water supplied tothe tube in accordance with a temperature within the tube, means forinjecting a slug of water into the tube at a point remote from saidinlet, and means for controlling the injection of the slug of water inaccordance with steam temperature in the tube.

6. A control for a flash boiler including a long tube adapted (to beheated, the control comprising means for injecting water into the tubeat one point to supply primary feed water and into the tube at anotherpoint to supply secondary feed water, and means for controlling theprimary water injection in accordance with a thermal condition withinthe tube between said points.

7. A control for a flash boiler having a long tube adapted to be heatedby a fire, the control comprising means for injecting primary feed waterinto one end of the tube, means for injecting secondary water into thetube at a point adjacent the other end of the tube, thermally responsivemeans for roughly coordinating the injection of the primary water withthe fire, and

means for coordinating the injection of secondlot that steam within aportion of the tube adjacent v to an outlet therefrom roughlyapproximates a desired temperature, means for injecting secondary waterinto said portion, and means for controlling the injection of saidsecondary water so that steam closely approximating a desiredtemperature is supplied.

9. The methodof operating a flash boiler having a long tube adapted tobe heated by a flre comprising introducing feed water into the tubeautomatically in variable quantities always substantially less than theequivalent steam demand and heat available so that steam within aportion of the boiler is at a higher temperature than a desiredtemperature, and introducing additional water into said portion inresponse to said higher temperature so that the steam tempera- 11. Aflash boiler control comprising a tube, means for heating said tube,means for introducing fluid into said tube between the ends thereof;means for introducing fluid into said tube at an end thereof,thermostatic means in said tube between the points of introduction offluid for controlling the introduction of fluid into said end of saidtube, and means responsive to the quantity of vapor discharging fromsaid tube for controlling the introduction of fluid into said end ofsaid tube WARREN DOBLE.

